Just a suggestion... as a longtime EIAS user (since 2.X days, this is the application that Cristobal is using in the tut) on the hunt for a new 3D package, I would say that the layer construct is very flawed and really was (is) the achilles heel of EIAS.

Better to adopt a (graphical) node based texturing system where nodes (fixed (bitmap) and calculated (shader)) can be inserted (placed) and connected freely to each other and to "output" nodes that drive the various material properties (ie Diffuse, Specular, Ambient, Geometry (bump & displace) Reflection (color and value), Transparency, Transmission (color and value), Luminance and Glow... whew!)

While a layer system is initially simple and intuitive (just pass up via modes like pshop) it requires all kinds of patches and tricks to jump around layers and to drive parameters in shaders further down in the layer list (AKA "reactive" ) and to patch values from one property to another. To make it really useful and flexible it become a semi threaded mess.
A node based system starts out a little more complex (a node chart required for each texture object) but is reasonable to do highly complex (and realistic) textures that are a combinations of of bit mapped and calculated (shader based) textures.